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When you think about it, it makes perfect sense; but the understanding took a long time coming. You can't preserve wild things unless you preserve their homes. If you take a butterfly like the sparklingly brilliant Adonis blue, for example, you have to have chalk or limestone grassland for it to survive, for that is where you will find its food plant, horseshoe vetch; if you take a bird like the Dartford warbler, you need a big patch of lowland heath, for it has learnt to specialise in catching the insects of heathland.

It's true that a few creatures are generalists, and can survive almost anywhere, but most have found their niche in specific biological circumstances, or habitats, as we now say; and without the habitat, you don't get the species, and that is a cast-iron rule. In fact, the leading cause of wildlife loss across the globe is habitat destruction; orang-utans are disappearing from much of their homeland in Indonesia not because they are being shot in great numbers, as they were in the 19th century, but because the rainforests where they live are being cut down and turned into oil-palm plantations.

It seems such a simple insight, in a way, but for centuries, nobody saw it, and even early conservationists didn't get the connection; the women who founded the Royal Society for the Protection of Birds in the 1890s just wanted to stop wild birds such as great crested grebes being killed for their feathers (used in women's hats), and to stop birds' eggs being collected; habitats were a closed book to them. It wasn't until 100 years ago next week, on 16 May 1912, that the idea that you needed to save places, if you wanted to save species, was suddenly brought into focus, by a remarkable man.

He was Charles Rothschild, a scion of what was then the richest family in the world. In the 19th century the Rothschild banking dynasty had achieved financial pre-eminence right across Europe. Charles's father Nathaniel, the first Lord Rothschild, was head of the English branch but his two sons, although they both followed him into the bank, were far more interested in natural history.

Walter Rothschild, the elder boy and subsequently the second Lord Rothschild, pursued an astonishing career of collecting natural history specimens. In his private museum in Tring, Hertfordshire, he amassed more than two million pinned butterflies and 30,000 beetles, as well as 300,000 bird skins, 200,000 birds' eggs and thousands of other specimens of fishes, reptiles and mammals from all over the world. You can still see many of them at the museum today (although not the stuffed birds).

Charles, his younger brother, was more solid in his achievements – he was a success in the bank, which Walter was forced to leave – but he was no less passionate about nature, especially entomology. Insects were his passion (he dreamed of becoming a professional entomologist) and he wrote his first scientific paper, on moths and butterflies, while still at school, but his real speciality was fleas: he became the world's leading expert and assembled a collection of more than a million (now in the British museum) as well as building formidable collections of butterflies and moths, and an expert knowledge of wild flowers.

Sometime in the early years of the 20th century, Charles Rothschild began to understand that the actual wildlife-rich places in the English countryside where he collected many of his specimens – what he termed his "good spots" – needed to be preserved. He had already begun to see the value of safeguarding sites, having bought Wicken Fen in Cambridgeshire, one of the last surviving examples of unspoiled fenland landscape, in 1899 (at the age of 22) and presented it to the National Trust: it was Britain's first nature reserve.

In 1910 he went further and bought another wild fenland remnant, Woodwalton Fen, as his personal reserve; he built a cottage on stilts in the heart of the fen as a base for his collecting expeditions, including moth trapping at night.

Eventually, it dawned on him – the first time that it had dawned on anybody – that there could be a whole network of such protected sites across the country, and in May 1912 he convened a meeting at the British Museum of like-minded enthusiasts, all of them highly influential, which led to the formation of the Society for the Promotion of Nature Reserves (SPNR).

The idea was that the society would identify places which needed protection, and encourage landowners and others to carry it out; and by 1915 a list of 284 proposed nature reserves in the UK had been compiled – moors and meadows, downs and commons, woods and fens – with 182 of them in England.

This list, "Rothschild's reserves" as it is sometimes known, represents the beginnings of organised nature conservation in Britain. What it has become, greatly expanded a century later, is essentially the vast network of 2,300 reserves run by the UK's 47 county wildlife trusts, since the SPNR, after a long hiatus caused by the two world wars and Charles Rothschild's early death, eventually morphed into the Wildlife Trusts Partnership. What we have now is a substantial list of individual sites where species are protected, from the swallowtail butterfly of Hickling Broad, guarded by the Norfolk Wildlife Trust, to the pine martens of Ben Mor Coigach, the mountain landscape in north-west Scotland which the Scottish Wildlife Trust watches over.

The range is massive: the islands of Skomer and Skokholm, managed by the Wildlife Trust of South and West Wales, look after the largest concentrations of Manx shearwaters in the world, whereas at Upton Heath in Dorset, the Dorset Wildlife Trust is preserving the rare smooth snake. Not far away, the Hampshire Wildlife Trust keeps the endangered musk orchid safe at Noar Hill near Selborne, while in the North, the Wildlife Trust for Lancashire, Manchester and North Merseyside is busy looking after uncommon natterjack toads on Ainsdale Dunes, between Liverpool and Southport.

The understanding of the habitat-species dependency is at the heart of all this, but now the trusts have a new vision for the future: conservation at the landscape scale.

Increasingly over recent decades, while special habitats for endangered creatures have been successfully saved, the wider countryside outside these protected areas has greatly suffered, not least from intensive farming, and natural habitats have been lost on an unprecedented scale.

Now in its Living Landscape programme, the Wildlife Trusts want to restore wildlife-richness to much wider areas, such as whole-river catchments, or tracts of upland. The idea is to recreate damaged habitats and link them through natural landscape corridors, not least because some species may need to migrate because of climate change; and further, to link restored areas to the green spaces and towns and cities, so that you can step outside your door, and wildlife is all around you.

More than 100 Living Landscape schemes are under way now across the whole of the UK, from Shakespeare's Forest of Arden, to the Itchen Valley in Hampshire. It is an inspiring step from Charles Rothschild's original insight that you have to preserve the homes of things; and the insect-mad banker would undoubtedly have approved.

Rare delights protecting Britain's natural wonders

Swallowtail butterfly, Hickling Broad, Norfolk

This extremely rare butterfly occurs in reed and sedge beds found within the Norfolk Broads, in areas protected by Norfolk Wildlife Trust, such as Hickling Broad. It has become increasingly rare because the British race of the butterfly feeds only on a single uncommon plant, milk parsley.

Manx Shearwater, Skomer and Skokholm, Wales

There are an estimated 120,000 breeding pairs of Manx shearwaters on Skomer and a further 45,000 pairs on Skokholm, off the coast of Pembrokeshire, making the two islands – both of which are managed by The Wildlife Trust of South and West Wales – the largest known concentration of this species in the world.

Smooth snake, Upton Heath, Dorset

Dorset Wildlife Trust has been working hard on Upton Heath, near Poole, to improve the heathland habitat for one of Britain's rarest reptiles, the smooth snake. It is only found in a small area of south-central England, centred in Hampshire and Dorset. (Upton Heath in fact holds all six British reptile species, three snakes and three lizards).

Natterjack toad, Ainsdale, Merseyside

The Wildlife Trust for Lancashire, Manchester and North Merseyside is involved in the management of sites along the Sefton Coast, north of Liverpool, where sand dunes are home to natterjack toads. The toads spawn in shallow dune pools which heat up quickly, meaning they hatch quickly compared with the rival common toad. The Trust is involved in ensuring areas of the dunes are not vegetated, making it easier for the natterjacks.

Musk orchid, Noar Hill, Hampshire

Noar Hill is a chalk grassland managed by Hampshire and Isle of Wight Wildlife Trust, well known for its wide range of orchid species, including the rare musk orchid. Noar Hill lies just above the Hampshire village of Selborne, as featured in the famous work by the naturalist Gilbert White, The Natural History and Antiquities of Selborne, published in 1789.

Pine marten, Ben Mor Coigach, Western Highlands

Following historical persecution, populations in Scotland of what many people consider our most charismatic mammal, the pine marten, are generally healthy and can be found in such places as the Ben Mor Coigach reserve, managed by the Scottish Wildlife Trust.